There Is Scouring Erosion Inside The Natural Gas‑fired Hot‑blast Stove. Which Castable Would You Recommend?

Solving Scour Problems for Natural‑Gas‑Fired Hot‑Blast Stoves! Selection Guide for These Castables for Your Reference!

In industrial production, natural‑gas‑fired hot‑blast stoves serve as core heat‑supply equipment, subject to continuous scouring by high‑temperature flue gas and dust‑laden gas all year round. Many enterprises are confronted with such troubles: frequent wear and spalling of castables on the hot‑blast stove lining. This not only impairs equipment operating efficiency, but also requires repeated shutdown for maintenance, raising production costs and even creating potential safety hazards.

In fact, scouring damage to hot‑blast stoves essentially results from mismatched castable selection for service conditions and inadequate construction work. Today, we will systematically sort out castable selection solutions for scouring conditions in natural‑gas‑fired hot‑blast stoves. Covering core product categories and precise application matching, this guide will help you thoroughly resolve this common industry pain point!

The scouring intensity of natural‑gas‑fired hot‑blast stoves is mainly determined by three major factors: temperature, gas flow velocity and dust content in flue gas. Clarify your actual service conditions before product selection to effectively avoid common pitfalls：

 Temperature range: The normal operating temperature is 800‑1200℃. Local areas such as around burners and combustion chamber outlets can reach 1300℃. A temperature margin of 50‑100℃ shall be reserved for the maximum service temperature of castables.

 Scouring grade: Duct elbows, reducers and nozzle outlets are high‑scouring zones; straight sections of main flue ducts and mixing chambers are medium‑to‑low scouring zones.

 Flue gas characteristics: For flue gas with high dust content, sulfur‑bearing or alkali‑containing dust, extra attention shall be paid to the anti‑erosion and anti‑slagging performance of castables.

Based on the above logic, castables featuring high abrasion resistance, good thermal shock resistance, high hot‑strength and volume stability shall be preferred. For high‑scouring zones, low‑cement or ultra‑low‑cement bonding systems must be adopted to greatly extend service life.

Preferred Grade: Corundum‑Based Abrasion‑Resistant Castable (Excellent Performance with Good Cost‑Performance)

1,High‑Alumina Corundum Low‑Cement Abrasion‑Resistant Castable (Al₂O₃ ≥ 70%‑80%)

Bonded with aluminate cement or low‑cement system, it balances abrasion resistance, thermal‑shock resistance and construction convenience. With moderate cost, it is suitable for large‑area installation. Its cold crushing strength after drying at 110℃ is ≥60 MPa, and the fired strength at 1100℃ can reach over 80 MPa. The abrasion loss is ≤8 cm³. It performs reliably under service conditions of 800‑1200℃ with medium dust content.

Application parts: Mixing chambers, straight sections of main flue ducts, hot‑blast outlets and other medium‑to‑high scouring zones. It is the conventional choice for most enterprises.

2,Corundum‑Mullite Low‑Cement Abrasion‑Resistant Castable (Al₂O₃ ≥ 80%‑85%)

Sintered mullite aggregate is added on the basis of corundum, and ultra‑low‑cement bonding technology is adopted. Compared with ordinary high‑alumina corundum castables, it delivers better abrasion resistance, superior thermal‑shock resistance and lower high‑temperature creep, and can withstand high‑temperature heavy scouring at 1000‑1300℃. Its cold crushing strength after firing at 1300℃ is ≥90 MPa, thermal‑shock stability (1100℃ → water‑cooling) ≥20 cycles, and abrasion loss ≤6 cm³, with overall upgraded performance.

Application parts: Areas around burner blocks, combustion chamber outlets, cyclone separator linings and other core zones with high‑temperature heavy scouring. It is especially suitable for service conditions featuring high gas flow velocity and large temperature fluctuation.

Supplementary Grade: Silicon‑Carbide Composite Abrasion‑Resistant Castable (For Extremely Severe Scouring Service)

For scenarios with extremely severe scouring accompanied by flue‑gas erosion (sulfur‑bearing and alkali‑containing dust), silicon‑carbide composite castable is the optimal solution. Silicon carbide features extremely high hardness, with far better abrasion resistance than corundum‑based materials. It also exhibits outstanding oxidation resistance and anti‑slagging performance, high thermal conductivity and excellent thermal‑shock resistance.

Selection key points: Prioritize corundum‑silicon carbide composite systems with SiC content of 15%‑25%, to avoid aggravated oxidation of pure silicon‑carbide materials above 1300℃. Adopt low‑cement or ultra‑low‑cement binders to balance hot‑strength and abrasion resistance.

Application parts: Duct elbows, tees, dip legs, areas around nozzles and other severely scoured zones, as well as service conditions with corrosive flue gas.

Warning Tip: Low‑Cement / Ultra‑Low‑Cement Bonding System Is Mandatory

Regardless of the aggregate‑based castable selected, ordinary cement‑bonded systems shall be avoided for all heavy‑scouring zones. Castables bonded by Low‑Cement Castable (LCC, cement content ≤8%) and Ultra‑Low‑Cement Castable (ULCC, cement content ≤3%) feature lower porosity, higher hot‑strength and superior spalling resistance, together with low drying shrinkage. They can fundamentally eliminate cracks and voids, which are the starting points of scouring damage.

Note: The water addition for such castables shall be strictly controlled within 5%‑7%. Vibration compaction is mandatory during construction. A slow heating‑up curve must be followed for drying to prevent bursting.

For quick and convenient matching, we have compiled grade‑selection solutions for key parts of hot‑blast stoves for your direct reference.

Selecting the right castable is only the first step. Construction quality directly determines service life. The following five key points must be strictly implemented:

 Anchor selection: For erosion zones, adopt V‑type / Y‑type heat‑resistant steel anchors of grade 0Cr25Ni20 or 1Cr18Ni9Ti, with a spacing of 200‑300 mm. Coat anchor surfaces with asphalt or refractory mortar to prevent high‑temperature oxidation.

 Construction compaction: Control water addition strictly in accordance with the manufacturer's requirements. Use vibrators for layered vibration compaction to avoid honeycombing and voids (such defects are major initiation points for erosion damage). For thick linings (>100 mm), construct in layers with each layer no thicker than 50 mm.

 Expansion joint arrangement: Install 5‑8 mm‑wide expansion joints every 2‑3 m, filled with ceramic fiber rope, to absorb high‑temperature thermal expansion stress and prevent castable cracking.

 Drying and curing: Follow the principle of "slow low‑temperature drying". Raise the temperature from ambient to 110 °C over 48‑72 hours. Avoid excessive heating‑up rates, which may cause rapid evaporation of internal moisture and lead to spalling. After drying, gradually increase temperature to operating temperature.

 Routine inspection: Regularly check the castable surface for cracks and spalling. Repair minor defects promptly with repair castables to prevent defect propagation and large‑area erosion damage.

Finally, this concise summary helps clarify thinking for quick castable selection:

 Moderate erosion, 800‑1200 °C: High‑Alumina Corundum Low‑Cement Abrasion‑Resistant Castable (Al₂O₃ ≥ 75%), cost‑effective first‑choice;

 High‑temperature severe erosion, 1000‑1300 °C: Corundum‑Mullite Low‑Cement Abrasion‑Resistant Castable (Al₂O₃ ≥ 82%), well‑rounded performance for full‑range matching;

 Extreme erosion plus flue‑gas attack: SiC‑Corundum Composite Abrasion‑Resistant Castable (SiC: 15%‑25%), for harsh service conditions.

Erosion issues in natural‑gas hot‑blast furnaces hinge on accurate material selection plus standardized construction. Proper castable selection can not only greatly extend equipment service life and cut maintenance costs, but also ensure continuous and stable production operation.